Alvin Ralph Eaton, an aerodynamics pioneer at The Johns Hopkins University Applied Physics Laboratory (APL) whose designs formed the basis for modern guided missile weapon systems, died Oct. 20. He was 91.

Mr. Eaton joined APL in September 1945, and built a distinguished 66-year career that continued until his death. He held numerous supervisory roles at the Laurel, Md. lab, including assistant director, head of the Fleet Systems Department, and assistant director for Tactical Systems. He formally retired from APL in 2002 but remained a consultant. In October 2010, Mr. Eaton received his 65-year service pin from APL, the first ever issued. "APL gave me the freedom to work on some incredible things," Eaton said at that time. "I always liked to solve problems."

In the late 1940s, Mr. Eaton discovered why the first supersonic surface-to-air missiles rolled unexpectedly at supersonic speeds — an anomaly that led to flight failures and nearly halted development of the program. He later recounted how, after being challenged to solve the problem by two colleagues one evening at a hotel bar in Texas, he solved the mystery by working out diagrams in pencil on a number of cocktail napkins. He woke his colleagues in the middle of the night and met them at the world's then-largest wind tunnel to demonstrate his discovery.

Soon after, Mr. Eaton invented and led the development of the unique tail-control aerodynamic configuration that enabled the development of supersonic interceptors, and is still used on many supersonic guided missiles. He directed the design, fabrication and tests of hardware for missiles employing tail control, and participated in the design of the first homing missiles. In 2008, Mr. Eaton was presented with the Missile Defense Agency's Technology Pioneer Award for Technical Achievement in Missile Defense.

"Those of us who had the good fortune to work with Al knew him as not only a man of great technical intellect, but also tremendous integrity and empathy for others," says Conrad Grant, head of APL's Air and Missile Defense Department. "This is a tremendous loss for his family and for his friends here at the Laboratory."

Mr. Eaton was born March 13, 1920, in Toledo, Ohio, where he graduated from Morrison R. Wait High School in 1937. He received a bachelor's degree in physics from Oberlin College in 1941, and a master's in aeronautical engineering from the California Institute of Technology in 1943.

Mr. Eaton's first project at APL was Bumblebee, a secret effort launched in the closing days of World War II to develop a supersonic, long-range, ramjet-powered antiaircraft missile for the defense of Navy vessels against attacks. The Terrier, Tartar and Talos missiles, which evolved into the current U.S. Navy Standard missile, were all developed based on the guided-missile principles discovered in the Bumblebee program.

Mr. Eaton designed, calibrated and supervised the Ordnance Aerophysics Laboratory Supersonic Wind Tunnel — the world's largest at that time — in Daingerfield, Texas, where he made his breakthrough. There, he led aerodynamics research and development of the earliest Navy surface-to-air guided missiles. In 1957, for contributions to the Terrier missile program and guided missile technology in general, he received the Navy Meritorious Public Service Citation.

Much of Mr. Eaton's work in following years remains classified, but was fundamental to advancing the state of the art of interceptor missiles used in ballistic missile defense.

Under Mr. Eaton's supervision, the Terrier and Tartar missile programs evolved into the Standard missile. Work on the Typhon Weapon System — incorporating a 360-degree phased array radar to detect and engage multiple targets and long ranges — was the precursor to the Aegis Weapon System, which is used on all U.S. Navy cruisers and destroyers today. Eaton conceived of the concept of force coordination and wrote the seminal paper in 1972 that led to establishment of the Battle Group Anti-Air Warfare Coordination Program, which spawned new concepts like the Cooperative Engagement Capability, distributed sensor and weapons coordination, and others.

Mr. Eaton devoted decades to the conception, development, evaluation, introduction and improvement of tactical systems for the Navy. During the Vietnam War, he served as the Navy's technical leader of countermeasures and tactics development. He oversaw work that reduced U.S. aircraft loss rates from 20 percent down to two percent, a decrease from hundreds of aircraft losses to only dozens. The tactics Mr. Eaton developed are still in use by Navy pilots today. For this work, in 1975 he received the U.S. Navy Distinguished Public Service Award.

In 1980, Mr. Eaton was named chairman of an independent review panel for the Patriot missile program by the assistant secretary of the Army. During his leadership of this group, Mr. Eaton helped guide the Patriot program and helped prevent its cancellation. This group also contributed important recommendations to the THAAD (Terminal High Altitude Area Defense) Program in its early development period. For these contributions, Mr. Eaton was awarded the U.S. Army Patriotic Civilian Service Award in 1995.

Mr. Eaton and his wife, Ellen, split their time between Clarksville, Md. and Hilton Head, SC. Other survivors include two sons, Eric and Alan; two grandchildren, Catherine and Carol; and four great grandchildren, Sean, Alyssa, Michael and Andrew.

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